[Bug c++/84813] [6/7 Regression] internal compiler error: Segmentation fault with lambdas and constexpr variables

["jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84813

Jakub Jelinek <jakub at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
                 CC|                            |jason at gcc dot gnu.org
   Target Milestone|---                         |6.5
            Summary|internal compiler error:    |[6/7 Regression] internal
                   |Segmentation fault with     |compiler error:
                   |lambdas and constexpr       |Segmentation fault with
                   |variables                   |lambdas and constexpr
                   |                            |variables

--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
The ICE started around r201080, but it isn't clear which exact revision. 
Initially it has been:
pr84813.C: In function ‘void apply()’:
pr84813.C:11:25: internal compiler error: tree check: expected lambda_expr,
have decltype_type in cp_parser_lambda_expression, at cp/parser.c:8520
   constexpr int N = T::N;
                         ^
0xf0a9ba tree_check_failed(tree_node const*, char const*, int, char const*,
...)
        ../../gcc/tree.c:9168
0x55211a tree_check(tree_node*, char const*, int, char const*, tree_code)
        ../../gcc/tree.h:3690
0x6a29a3 cp_parser_lambda_expression
        ../../gcc/cp/parser.c:8520
0x69b7bb cp_parser_primary_expression
        ../../gcc/cp/parser.c:4221
0x69e681 cp_parser_postfix_expression
        ../../gcc/cp/parser.c:5804
0x6a0aa7 cp_parser_unary_expression
        ../../gcc/cp/parser.c:7000
0x6a15fa cp_parser_cast_expression
        ../../gcc/cp/parser.c:7592
0x6a1668 cp_parser_binary_expression
        ../../gcc/cp/parser.c:7692
0x6a1d36 cp_parser_assignment_expression
        ../../gcc/cp/parser.c:7928
0x6a1fa0 cp_parser_expression
        ../../gcc/cp/parser.c:8090
0x6a21ad cp_parser_expression
        ../../gcc/cp/parser.c:8129
0x6a43b5 cp_parser_expression_statement
        ../../gcc/cp/parser.c:9384
0x6a404d cp_parser_statement
        ../../gcc/cp/parser.c:9235
0x6a49d3 cp_parser_statement_seq_opt
        ../../gcc/cp/parser.c:9509
0x6a48d4 cp_parser_compound_statement
        ../../gcc/cp/parser.c:9463
0x6b3431 cp_parser_function_body
        ../../gcc/cp/parser.c:18257
0x6b373a cp_parser_ctor_initializer_opt_and_function_body
        ../../gcc/cp/parser.c:18293
0x6ba671 cp_parser_function_definition_after_declarator
        ../../gcc/cp/parser.c:22271
0x6ba4c5 cp_parser_function_definition_from_specifiers_and_declarator
        ../../gcc/cp/parser.c:22192
0x6afbc2 cp_parser_init_declarator
        ../../gcc/cp/parser.c:16307
Starting with r210017 it segfaults in:
#0  0x0000000000c605e1 in pointer_map_insert (pmap=0x0, p=0x7fffefcfa260) at
../../gcc/pointer-set.c:226
#1  0x00000000005fe413 in register_local_specialization (spec=0x7fffefd0c688,
tmpl=0x7fffefcfa260) at ../../gcc/cp/pt.c:1731
#2  0x0000000000632299 in tsubst_decl (t=0x7fffefcfa260, args=0x7fffefcfea60,
complain=0) at ../../gcc/cp/pt.c:11135
#3  0x0000000000638e1b in tsubst_copy (t=0x7fffefcfa260, args=0x7fffefcfea60,
complain=0, in_decl=0x0) at ../../gcc/cp/pt.c:12636
#4  0x0000000000646e1c in tsubst_copy_and_build (t=0x7fffefcfa260,
args=0x7fffefcfea60, complain=0, in_decl=0x0, function_p=false, 
...
inside dump_decl from decl_as_dwarf_string called during dwarf2out_type_decl.
Obviously, we shouldn't try to do any tsubst during that.

The r251433 changes are not backportable though.